Using DynDNS or a similar service not only allows access to your home machine from outside without needing to know what IP the ISP has assigned to it but it also comes in handy if you want to know your external IP address. The only purpose of the sed command is to remove the leading "host.na.me has address " part from the output. If you don't need to discard it you can simply use
host $HOSTNAME

prints out the time for the timezone specified in $offsetutc. So you have less to think about things like: "I'm in utc+4 and my friend in utc-7, can I call him now or will I wake him?"
Note: $offsetutc should be an integer between -12 and 12.
Show Sample Output

sends commands specified in $commandfile to the telnet-server specified by $telnetserver.
to have newlines in $commandfile interpreted as ENTER, save the file in CR+LF (aka "Windows-Textfile") format.
if you want to save the output in a separate file, use:
nc $telnetserver 23 < $commandfile > $resultfile

A similar command that lists only the currently running VMs is thus:
VBoxManage list runningvms
...the above showing a list of VMs by name and UUID in the same format as the "$ VBoxManage list vms" command
Show Sample Output

you can launch a VirtualBox VM from the command line using VBoxManage, but that invokes it in a gui environment.
If you want to just fire off your VM in the background, use VBoxHeadless as shown. To get the names and UUIDs of your VirtualBox VMs, type:
VBoxManage list

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